Rm. Gunasekera et al., EFFECT OF DIETARY-PROTEIN LEVEL ON SPAWNING PERFORMANCE AND AMINO-ACID-COMPOSITION OF EGGS OF NILE TILAPIA, OREOCHROMIS-NILOTICUS, Aquaculture, 146(1-2), 1996, pp. 121-134
Oreochromis niloticus were maintained on three purified, isocalorific
diets of different dietary protein levels (10, 20 and 35%), with casei
n and gelatin as protein sources, The dietary protein influence on spa
wning interval, fecundity, relative fecundity (number of eggs per unit
weight) and egg size at four successive spawnings was investigated. T
he protein, moisture, free and bound amino acid composition of the spa
wned eggs were determined. O. niloticus females fed 20 and 35% protein
levels maintained their spawning cycle, whereas at 10% spawning inter
vals were prolonged after about 4 months of feeding. Females fed 20 an
d 35% protein diets produced a higher number of eggs per spawn than th
ose fed 10%, especially at later spawnings, But relative fecundity and
egg size did not differ significantly between the treatments. The amo
unt of protein in eggs of females maintained on 35% protein diet was s
ignificantly higher than in others, However, the moisture content of t
he eggs did not vary among the diets. Of the free amino acids, methion
ine, valine, tyrosine, serine, glycine and proline were influenced by
the dietary regime. The total (free + protein bound) individual amino
acids in the eggs were not affected by dietary protein level. However,
the total overall amino acid pool of eggs in the 35% protein level wa
s higher than in the others.